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engineering
mechanical engineering
Principles of heat transfer 7th Edition Frank Kreith, Raj M. Manglik, Mark S. Bohn - Solutions
In Problem 14.37, NO2 transport by diffusion in a stagnant atmosphere was considered for steady-state conditions. However, the problem is actually time dependent, and a more realistic approach would account for transient effects. Consider the ground level emission of NO2 to begin in the early
A large sheet of material 40 mm thick contains dissolved hydrogen (H2) having a uniform concentration of 3k mol/m3. The sheet is exposed to a fluid stream that causes the concentration of the dissolved hydrogen to be reduced suddenly to zero at both surfaces. This surface condition is maintained
A common procedure for increasing the moisture content of air is to bubble it through a column of water. Assume the air bubbles to be spheres of radius r0 = 1 mm and to be in thermal equilibrium with the water at 25°C. How long should the bubbles remain in the water to achieve a vapor
Steel is carburized in a high-temperature process that depends on the transfer of carbon by diffusion. The value of the diffusion coefficient is strongly temperature dependent and may be approximated as DC – (m2/s) ≈ 2 x 10-5 exp [- 17,000/T (K)]. If the process is effected at 1000°C and a
A thick plate of pure iron at 1000°C is subjected to a carburization process in which the surface of the plate is suddenly exposed to a gas that induces a carbon concentration Cc,s at one surface. The average diffusion coefficient for carbon and iron at this temperature is DC-Fe = 3 x 10-11 m2/s.
A solar pond operates on the principle that heat losses from a shallow layer of water, which acts as a solar absorber, may be minimized by establishing a stable vertical salinity gradient in the water. In practice such a condition may be achieved by applying a layer of pure salt to the bottom and
If an amount of energy Q''o (J/m2) is released instantaneously, as, for example, from a pulsed laser, and it is absorbed by the surface of a semi-infinite medium, with no attendant losses to the surroundings, the subsequent temperature distribution in the medium is where Ti is the initial, uniform
The presence of CO2 in solution is essential to the growth of aquatic plant life, with CO2 used as a reactant in the photosynthesis. Consider a stagnant body of water in which the concentration of CO2 (PA) is everywhere zero. At time t = 0, the water is exposed to a source of CO2, which maintains
Hydrogen gas is used in a process to manufacture a sheet material of 6-mm thickness. At the end of the process, H2 remains in solution in the material with a uniform concentration of 320 k mol/m3. To remove H2 from the material, both surfaces of the sheet are exposed to an air stream at 500 K and a
Consider the hydrogen-removal process described in Problem 14.46, but under conditions for which the mass diffusivity of the hydrogen gas (A) in the sheet material (B) is DAB = 1.8 x 10-11 m2 /s (instead of 2.6 x 10-8 m2/s). With the smaller value of DAB' a uniform concentration may no longer be
A 1-mm-thick square (100 mm x 100 mm) sheet of polymer is suspended from a precision scale in a chamber characterized by a temperature and relative humidity of T = 300 K and cp = 0, respectively. Suddenly, at time t = 0, the chamber's relative humidity is raised to cp = 0.95. The measured mass of
Consider a DVD similar to that of Problem 5.86. To protect sensitive information within the storage medium, a very thin film of reactive polymer is embedded within the polycarbonate at a distance d = 0.5 mm from the surface. The thin film can undergo a chemical reaction with oxygen during which it
Consider the DVD of Problem 14.49, except now the reacting polymer is blended uniformly with the polycarbonate to reduce manufacturing costs. Assume that a first-order homogeneous chemical reaction takes place between the polymer and oxygen; the reaction rate is proportional to the oxygen molar
A vitreous silica optical fiber of diameter 100μm is used to send optical signals from a sensor placed deep inside a hydrogen chamber. The hydrogen is at a pressure of 20 bars. The mass diffusivity and solubility of the hydrogen in the glass fiber are DAB = 2.88 x 10-15 m2/s and S = 4.15 x 10-3k
The surface of glass quickly develops very small micro cracks when exposed to high humidity. Although micro cracks can be safely ignored in most applications, they can significantly decrease the mechanical strength of very small glass structures such as optical fibers. Consider a glass optical
A person applies an insect repellent onto an exposed area of A = 0.5 m2 of their body. The mass of spray used is M = 10grams and the spray contains 25% (by mass) active ingredient. The inactive ingredient quickly evaporates from the skin surface.(a) If the spray is applied uniformly and the density
Show that the coefficient of thermal expansion for an ideal gas is 1/T, where T is the absolute temperature.GIVENIdeal gasAbsolute temperature = T
Calculate the coefficient of thermal expansion, β, for saturated water at 403 K from its definition and property values in Appendix 2, Table 13. Then compare your results with the value in the table.GIVENSaturated water at 400 K
Calculate the coefficient of thermal expansion, β, from its definition for steam at 450?C and pressures of 0.1 atm and 10 atm from standard steam tables. Then compare your results with the value obtained by assuming that steam is a perfect gas and explain the difference.GIVENSteamTemperature =
A long cylinder of 0.1 m diameter has a surface temperature of 400 K. If it is immersed in a fluid at 350 K, natural convection will occur as a result of the temperature difference. Calculate the Grashof and Rayleigh numbers that will determine the Nusselt number if the fluid is(a) Nitrogen(b)
For the conditions given in Problem 5.4, determine the Nusselt Number and the heat transfer coefficient from Figure.From Problem 5.4: A long cylinder of 0.1 m diameter has a surface temperature of 400 K. If it is immersed in a fluid at 350 K, natural convection will occur as a result of the
An empirical equation proposed for the heat transfer coefficient in natural convection from long vertical cylinders to air at atmospheric pressure is Where T = the film temperature = 1/2 (Ts + T??) and T is in the range 0 to 200?C The corresponding equation in dimensionless form is By comparing
Solar One is the first large-scale (10 MW electric) solar-thermal electric-power-generating plant in the U.S. It is located near Barstow, CA. A schematic diagram of the receiver and tower is shown below (the heliostat, i.e., mirror field, is not shown). The receiver may be treated as a cylinder 7 m
Compare the rate of heat loss from a human body with the typical energy intake from consumption of food (1033 kcal/day). Model the body as a vertical cylinder 30 cm in diameter and 1.8 m high in still air. Assume the skin temperature is 2?C below normal body temperature. Neglect radiation,
An electric room heater has been designed in the shape of a vertical cylinder 2 m tall and 30 cm in diameter. For safety, the heater surface cannot exceed 35?C. If the room air is 20?C, find the power rating of the heater in watts.GIVENAn electric heater in the shape of a vertical cylinderHeater
Consider a design for a nuclear reactor using natural-convection heating of liquid bismuth. The reactor is to be constructed of parallel vertical plates 6 ft tall and 4 ft wide, in which heat is generated uniformly. Estimate the maximum possible heat dissipation rate from each plate if the average
A mercury bath at 60?C is to be heated by immersing cylindrical electric heating rods, each 20 cm tall and 2 cm in diameter. Calculate the maximum electric power rating of a typical rod if its maximum surface temperature is 140?C.GIVENCylindrical heating rods in a mercury bathMercury temperature
An electric heating blanket is subjected to an acceptance test. It is to dissipate 400 W on the high setting when hanging in air at 20?C. If the blanket is 1.3 m wide:(a) What is the length required if its average temperature at the high setting is to be 40?C, and(b) If the average temperature at
An aluminum sheet, 0.4 m tall, 1 m long, and 0.002 m thick is to be cooled from an initial temperature of 150?C to 50?C by immersing it suddenly in water at 20?C. The sheet is suspended from two wires at the upper corners.(a) Determine the initial and the final rate of heat transfer from the
A 0.1 cm thick flat copper plate, 2.5 m x 2.5 m square is to be cooled in a vertical position. The initial temperature of the plate is 90?C with the ambient fluid at 30?C. The fluid medium is either atmospheric air or water.(a) Calculate the Grashof numbers(b) Determine the initial heat transfer
A laboratory apparatus is used to maintain a horizontal slab of ice at 28?F so that specimens can be prepared on the surface of the ice and kept close to 32?F. If the ice is 4 in. by 1.5 in and the laboratory is kept at 60?F, find the cooling rate in watts that the apparatus must provide to the
An electronic circuit board is the shape of a flat plate 0.3 m x 0.3 m in plan-form and dissipates 15 W. It may be placed in operation on an insulated surface in a horizontal position or at an angle of 45 degrees to horizontal, both in still air at 25°C. If the circuit would fail above 60°C,
Cooled air is flowing through a long sheet metal air conditioning duct, 0.2 m high and 0.3 m wide. If the duct temperature is 10?C and passes through a crawl space under a house at 30?C, estimate(a) The heat transfer rate to the cooled air per meter length of duct.(b) The additional air
Solar radiation at 600 W/m2 is absorbed by a black roof inclined at 30?C as shown. If the underside of the roof is well insulated, estimate the maximum roof temperature in 20?C air.GIVENInclined roof, well insulated on the undersideIncline angle (θ) = 30 degreesAir temperature = 20?CSolar
A 1 m square copper plate is placed horizontally on 2 m high legs. The plate has been coated with a material that provides a solar absorptance of 0.9 and an infrared emittance of 0.25. If the air temperature is 30?C, determine the equilibrium temperature on an average clear day in which the solar
A 2.5 x 2.5 m steel sheet 1.5 mm thick is removed from an annealing oven at a uniform temperature of 425?C and placed in a large room at 20?C in a horizontal position.(a) Calculate the rate of heat transfer from the steel sheet immediately after its removal from the furnace, considering both
A thin electronic circuit board, 0.1 m by 0.1 m in size, is to be cooled in air at 25?C. The board is placed in a vertical position and the back side is well insulated. If the heat dissipation is uniform at 200 W/m2, determine the average temperature of the surface of the board cover.GIVENVertical
A plot of coffee has been allowed to cool to 17?C. If the electrical coffee maker is turned back on, the hot plate on which the pot rests is brought up to 70?C immediately and held at that temperature by a thermostat. Consider the pot to be a vertical cylinder 130 mm in diameter and the depth of
A laboratory experiment has been performed to determine the natural-convection heat transfer correlation for a horizontal cylinder of elliptical cross section in air. The cylinder is 1 m long, has a hydraulic diameter of 1 cm, a surface area of 0.0314 m2, and is heated internally by electrical
A long, 2-cm-OD horizontal copper pipe carries dry saturated steam at 1.2 atm absolute pressure. The pipe is contained within an environmental testing chamber in which the ambient air pressure can be adjusted from 0.5 to 2.0 atm, absolute while the ambient air temperature is held constant at 20?C.
Compare the rate of condensate flow from the pipe in Problem 5.24 (air pressure = 2.0 atm) with that for a 3.89-cm-OD pipe and 2.0 atm air pressure. What is the rate of condensate flow if the 2 cm pipe is submerged in a 20°C constant-temperature water bath?From Problem 5.24: Long, 2-cm-OD
A thermocouple (0.8 mm OD) is located horizontally in a large enclosure whose walls are at 37?C. The enclosure is filled with a transparent quiescent gas which has the same properties as air. The electromotive force (emf) of the thermocouple indicates a temperature of 230?C. Estimate the true gas
Only 10 percent of the energy dissipated by the tungsten filament of an incandescent lamp is in the form of useful visible light. Consider a 100 W lamp with a 10 cm spherical glass bulb. Assuming an emissivity of 0.85 for the glass and ambient air temperature of 20?C, what is the temperature of the
A sphere 20 cm in diameter containing liquid air (??140?C) is covered with 5 cm thick glass wool (50 kg/m3 density) with an emissivity of 0.8. Estimate the rate of heat transfer to the liquid air from the surrounding air at 20?C by convection and radiation. How would you reduce the heat
A 2-cm-OD bare aluminum electric power transmission line with an emissivity of 0.07 carries 500 amps at 400 kV. The wire has an electrical resistivity of 1.72 micro-ohms cm2/cm at 20?C and is suspended horizontally between two towers separated by 1 km. Determine the surface temperature of the
An 8-in.-OD horizontal steam pipe carries 220 lbm/h dry saturated steam at 250°F. If ambient air temperature is 70°F, determine the rate of condensate flow at the end of 10 ft of pipe. Use an emissivity of 0.85 for the pipe surface. If it is desired to keep heat losses below 1 percent of the rate
A long steel rod (2 cm in diameter, 2 m long) has been heat-treated and quenched to a temperature of 100°C in an oil bath. In order to cool the rod further it is necessary to remove it from the bath and expose it to room air. Will the faster cool-down result from cooling the cylinder in the
In petroleum processing plants, it is often necessary to pump highly viscous liquids such as asphalt through pipes. In order to keep pumping costs within reason, the pipelines are electrically heated to reduce the viscosity of the asphalt. Consider a 15-cm-OD uninsulated pipe and an ambient
Estimate the rate of convective heat transfer across a 1 m tall double-pane window assembly in which the outside pane is at 0°C and the inside pane is at 20°C. The panes are spaced 2.5 cm apart. What is the thermal resistance (‘R’ value) of the window if the rate of radiative heat flux is 84
An architect is asked to determine the heat loss through a wall of a building constructed as shown in the sketch. If the wall spacing is 10 cm, the inner surface is at 20°C and the outer surface is at – 8°C with air between,(a) Estimate the heat loss by natural convection. Then determine the
A flat plate solar collector of 3 m x 5 m area has an absorber plate that is to operate at a temperature of 70?C. To reduce heat losses, a glass cover is placed 0.05 m from the absorber and its operating temperature is estimated at 35?C. Determine the rate of heat loss from the absorber if the 3 m
Determine the rate of heat loss through a double glazed window, as shown in the sketch, if the inside room temperature is 65?C and the average outside air is 0?C during December. Neglect the effect of the window frame. If the house is electrically heated at a cost of $0.06/(kW hr), estimate the
Calculate the rate of heat transfer between a pain of concentric horizontal cylinders 20 mm and 126 mm in diameter. The inner cylinder is maintained at 37°C and the outer cylinder is maintained at 17°C.GIVENConcentric cylindersSmaller diameter (Di) = 20 mm = 0.02 mLarger diameter (Do) = 126 mm =
Two long concentric horizontal aluminum tubes of 0.2 m and 0.25 m diameter are maintained at 300 K and 400 K respectively. The space between the tubes is filled with nitrogen. If the surfaces of the tubes are polished to prevent radiation, estimate the rate of heat transfer for gas pressure of (a)
A solar collector design consists of several parallel tubes each enclosed concentrically in an outer tube which is transparent to solar radiation. The tubes are thin walled with diameter of the inner and outer cylinders of 0.10 and 0.15 m respectively. The annular space between the tubes is filled
Liquid oxygen at ?? 183?C is stored in a thin walled spherical container with an outside diameter of 2 m. This container is surrounded by another sphere of 2.5 m inside diameter to reduce heat loss. The inner spherical surface has an emissivity of 0.05 and the outer sphere is black. Under normal
The surfaces of two concentric spheres having radii of 75 and 100 mm are maintained at 325 K and 275 K, respectively.(a) If the space between the spheres is filled with nitrogen at 5 atm, estimate the convection heat transfer rate.(b) If both sphere surfaces are black, estimate the total rate of
Estimate the rate of heat transfer from one side of a 2 m diameter disk rotating at 600 rev/min in 20?C air, if its surface temperature is 50?C.GIVENA disk rotating in airDiameter (D) = 2 mRotational speed (w) = 600 rev/minAir temperature (T??) = 20?CSurface temperature (Ts) = 50?CASSUMPTIONSThe
A sphere 0.1 m diameter is rotating at 20 RPM in a large container of CO2 at atmospheric pressure. If the sphere is at 60?C and the CO2 at 20?C, estimate the rate of heat transfer.GIVENA rotating sphere in carbon dioxide at atmospheric pressureDiameter (D) = 0.1 mSpeed of rotation (w) = 20
A mild steal (1% carbon), 2 cm OD shaft, rotating in 20?C air at 20,000 rev/min, is attached to two bearings 0.7 m apart. If the temperature at the bearings is 90?C, determine the temperature distribution along the shaft. Hint: Show that for the high rotational speeds equation (5.35) approaches:
An electronic device is to be cooled in air at 20?C by an array of equally spaced vertical rectangular fins as shown in the sketch below. The fins are made of aluminum and their average temperature, Ts, is 100?C.Estimate(a) The optimum spacing, s(b) The number of fins(c) The rate of heat transfer
Consider a vertical 20 cm tall flat plate at 120?C suspended in a fluid at 100?C. If the fluid is being forced past the plate from above, estimate the fluid velocity for which natural convection becomes negligible (less than 10%) in:(a) Mercury(b) Air(c) Water.GIVENA vertical flat plate suspended
Suppose a thin vertical flat plate. 60 cm high and 40 cm wide, is immersed in a fluid flowing parallel to is surface. If the plate is at 40?C and the fluid at 10?C, estimate the Reynolds number at which buoyancy effects are essentially negligible for heat transfer from the plate if the fluid is:(a)
A vertical isothermal plate 30 cmhigh is suspended in an atmosphere air streamflowing at 2 m/s in a vertical direction. If the air is at 16?C, estimate the plate temperature for which the natural-convection effect on the heat transfer coefficient will be less than 10 percent.GIVENA vertical
A horizontal disk 1 m in diameter rotates in air at 25?C. If the disk is at 100?C, estimate the RPM at which natural convection for a stationary disk becomes less than 10% of the heat transfer for a rotating disk.GIVENA rotating horizontal disk in airDiameter (D) = 1 mAir temperature (T??) =
The refrigeration system for an indoor ice rink is to be sized by an HVAC contractor. The refrigeration system has a COP (coefficient of performance) of 0.5. The ice surface is estimated to be ??2?C and the ambient air is 24?C. Determine the size of the refrigeration system in kW required for a 110
A 0.15 m square circuit board is to be cooled in a vertical position as shown. The board is insulated on one side while on the other, 100 closely spaced square chips are mounted, each of which dissipated 0.06 W of heat. The board is exposed to air at 25?C and the maximum allowable chip temperature
A gas-fired industrial furnace is used to generate steam. The furnace is a 3 m cubic structure and the interior surfaces are completely covered with boiler tubes transporting pressurized wet steam at 150°C. It is desired to keep the furnace losses to 1% of the total heat input of 1 MW. The outside
An electronic device is to be cooled by natural convection in atmospheric air at 20?C. The device generates internally 50 W and only one of its external surfaces is suitable for attaching fins. The surface available for attaching cooling fins is 0.15 m tall and 0.4 m wide. The maximum length of a
To measure the mass flow rate of a fluid in a laminar flow through a circular pipe, a hot wire type velocity meter is placed in the center of the pipe. Assuming that the measuring station is far from the entrance of the pipe, the velocity distribution is parabolic, or where Umax is the centerline
Nitrogen at 30?C and atmospheric pressure enter a triangular duct 0.02 m on each side at a rate of 4 x 10??4 kg/s. If the duct temperature is uniform at 200?C, estimate the bulk temperature of the nitrogen 2 m and 5 m from the inlet.GIVENAtmospheric nitrogen flowing through a triangular ductBulk
Air at 30?C enters a rectangular duct 1 m long and 4 mm by 16 mm in cross-section at a rate of 0.0004 kg/s. If a uniform heat flux of 500 W/m2 is imposed on both of the long sides of the duct, calculate(a) The air outlet temperature(b) The average duct surface temperature, and(c) The pressure
Engine oil flows at a rate of 0.5 kg/s through a 2.5 cm ID tube. The oil enters 25?C while the tube wall is at 100?C.(a) If the tube is 4 m long. Determine whether the flow is fully developed.(b) Calculate the heat transfer coefficient.GIVENEngine oil flows through a tubeMass flow rate (m) = 0.5
The equation was recommended by H. Hausen (Zeitschr. Ver. Deut. Ing., Belherft No. 4, 1943) for forced-convection heat transfer in fully developed laminar flow through tubes. Compare the values of the Nusselt number predicted by Hausen??s equation for Re = 1000, Pr = 1, and L/D = 2, 10 and 100,
Air at an average temperature of 150?C flows through a short square duct 10 x 10 x 2.25 cm at a rate of 15 kg/h. The duct wall temperature is 430?C. Determine the average heat transfer coefficient, using the duct equation with appropriate L/D correction. Compare your results with
Water enters a double pipe heat-exchanger at 60?C. The water flows on the inside through a copper tube 2.54 cm (1 in) ID at a velocity of 2 cm/s. Steam flows in the annulus and condenses on the outside of the copper tube at a temperature of 80?C. Calculate the outlet temperature of the water if the
An electronic device is cooled by passing air at 27?C through six small tubular passages in parallel drilled through the bottom of the device as shown below. The mass flow rate per tube is 7 x 10??5 kg/s.Heat is generated in the device resulting in approximately uniform heat flux to the air in the
Unused engine oil with a 100?C inlet temperature flows at a rate of 250 g/sec through a 5.1-cm-ID pipe that is enclosed by a jacket containing condensing steam at 150?C. If the pipe is 9 m long, determine the outlet temperature of the oil.GIVENUnused engine oil flows through a pipe enclosed by a
Determine the rate of heat transfer per foot length to a light oil flowing through a 1-in.-ID, 2-ft-long copper tube at a velocity of 6 fpm. The oil enters the tube at 60?F and the tube is heated by steam condensing on its outer surface at atmospheric pressure with a heat transfer coefficient of
Calculate the Nusselt number and the convection heat transfer coefficient by three different methods for water at a bulk temperature of 32?C flowing at a velocity of 1.5 m/s through a 2.54-cm-ID duct with a wall temperature of 43?C. Compare the results.GIVENWater flowing through a ductBulk water
Atmospheric pressure air is heated in a long annulus (25 cm ID, 38 cm OD) by steam condensing at 149?C on the inner surface. If the velocity of the air is 6 m/s and its bulk temperature is 38?C, calculate the heat transfer coefficient.GIVENAtmospheric flow through an annulus with steam condensing
If the total resistance between the steam and the air (including the pipe wall and scale on the steam side) in Problem 6.12 is 0.05 m2 K/W, calculate the temperature difference between the outer surface of the inner pipe and the air. Show the thermal circuit. From Problem 6.12: In a long annulus
Atmospheric air at a velocity of 61 m/s and a temperature of 16°C enters a 0.61-m-long square metal duct of 20
Compute the average heat transfer coefficient hc for 10?C water flowing at 4 m/s in a long, 2.5-cm-ID pipe (surface temperature 40?C) by three different equations and compare your results. Also determine the pressure drop per meter length of pipe.GIVENWater flowing through a pipeWater temperature
Water at 80?C is flowing through a thin copper tube (15.2 cm ID) at a velocity of 7.6 m/s. The duct is located in a room at 15?C and the heat transfer coefficient at the outer surface of the duct is 14.1 W/(m2 K). (a) Determine the heat transfer coefficient at the inner surface. (b) Estimate the
Mercury at an inlet bulk temperature of 90?C flows through a 1.2-cm-ID tube at a flow rate of 4535 kg/h. This tube is part of a nuclear reactor in which heat can be generated uniformly at any desired rate by adjusting the neutron flux level. Determine the length of tube required to raise the bulk
Exhaust gases having properties similar to dry air enter a thin-walled cylindrical exhaust stack at 800 K. The stack is made of steel and is 8 m tall and 0.5 m inside diameter. If the gas flow rate is 0.5 kg/s and the heat transfer coefficient at the outer surface is 16 W/(m2 K), estimate the
Water at an average temperature of 27°C is flowing through a smooth 5.08-cm-ID pipe at a velocity of 0.91 m/s. If the temperature at the inner surface of the pipe is 49°C, determine (a) the heat transfer coefficient, (a) The rate of heat flow per meter of pipe, (b) The bulk temperature rise per
An aniline-alcohol solution is flowing at a velocity of 10 fps through a long, 1-in.-ID thin wall tube. On the outer surface of the tube, steam is condensing at atmospheric pressure, and the tube-wall temperature is 212?F. The tube is clean, and there is no thermal resistance due to a scale deposit
In a refrigeration system, brine (10 percent NaCl) by weight having a viscosity of 0.0016 (Ns)/m2 and a thermal conductivity of 0.85 W/(m K) is flowing through a long 2.5-cm-ID pipe at 6.1 m/s. Under these conditions, the heat transfer coefficient was found to be 16,500 W/(m2 K). For a brine
Derive an equation of the form hc = f(T, D, V) for turbulent flow of water through a long tube in the temperature range between 20? and 100?C.GIVENTurbulent water flow through a long tubeWater temperature range (Tb) = 20?C to 100?CASSUMPTIONSSteady stateVariation of properties with temperature can
The intake manifold of an automobile engine can be approximated as a 4 cm ID tube, 30 cm in length. Air at a bulk temperature of 20?C enters the manifold at a flow rate of 0.01 kg/s. The manifold is a heavy aluminum casting and is at a uniform temperature of 40?C. Determine the temperature of the
High-pressure water at a bulk inlet temperature of 93?C is flowing with a velocity of 1.5 m/s through a 0.015-m-diameter tube, 0.3 m long. If the tube wall temperature is 204?C, determine the average heat transfer coefficient and estimate the bulk temperature rise of the water.GIVENWater flowing
Suppose an engineer suggests that air is to be used instead of water in the tube of Problem 6.24 and the velocity of the air is to be increased until the heat transfer coefficient with the air equals that obtained with water at 1.5 m/s. Determine the velocity required and comment on the feasibility
Atmospheric air at 10?C enters a 2 m long smooth rectangular duct with a 7.5 cm x 15 cm cross-section. The mass flow rate of the air is 0.1 kg/s. If the sides are at 150?C, estimate(a) The heat transfer coefficient,(b) The air outlet temperature,(c) The rate of heat transfer, and(d) The pressure
Air at 16?C and atmospheric pressure enters a 1.25-cm-ID tube at 30 m/s. For an average wall temperature of 100?C, determine the discharge temperature of the air and the pressure drop if the pipe is (a) 10 cm long and (b) 102 cm long.GIVENAtmospheric air flowing through a tubeEntering air
The equation has been proposed by Hausen for the transition range (2300 GIVENWater flowing through a pipeThe Hausen correlation given aboveWater temperature = 15?CPipe temperature = 100?CASSUMPTIONSSteady stateConstant and uniform pipetemperature
Water at 20°C enters a 1.91 cm ID, 57 cm long tube at a flow rater of 3 gm/s. The tube wall is maintained at 30°C. Determine the water outlet temperature. What error in the water temperature results if natural convection effects are neglected? GIVENWater flowing through a tubeEntering water
A solar thermal central receiver generates heat by focusing sunlight with a field of mirrors on a bank of tubes through which a coolant flows. Solar energy absorbed by the tubes is transferred to the coolant which can then deliver useful heat to a load. Consider a receiver fabricated from multiple
Determine the heat transfer coefficient for liquid bismuth flowing through an annulus (5 cm ID, 6.1 cm OD) at a velocity of 4.5 m/s. The wall temperature of the inner surface is 427°C and the bismuth is at 316°C. It may be assumed that heat losses from the outer surface are negligible.GIVENLiquid
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